The course website and blog for the Fall 2015 instance of Penn State's SC200 course

Tag Archives: lunatic

This blog is a continuation of a topic discussed in Does the Moon Really Make You Crazy? Part 1. Make sure to pop on over to that blog first to set the scene and get some interesting statistics regarding the moon and crime rates. If you don’t have time to read the whole thing, at least take a look at the last few paragraphs. Today’s blog is looking at a few other aspects of the lunar effect on behavior.

Background

In my previous blog on this topic two studies showed a correlation between the frequency of certain types of crime and the phase of the moon. In this blog I will be looking at other ways the moon might influence behaviors like investment decisions and aggression. If market behavior is based more on emotion during the full moon, and aggressive impulses are also increased, it may be a sign that there is something to this moon theory.

The Moon and the Stock Market

“Moon Phase Effect on Investor Psychology and Stock Trading Performance” explores the connection between the full moon and investor performance. Basically the scientists were asking “Does a full moon mean less money and more aggressive behavior?” The short answer to that question in this study is yes. But before we take that data at face value, lets look a little bit at the methods. The study’s conclusion is based off of 202 Malyasian investors. This seems like a reasonable number to look at though, although it is important to note that some of the original subjects were dropped from the study for dissimilarities or failure to complete both periods of observation. This may create a bias towards responsible investors and ruin any randomization. This study was a prospective observational study that used surveys and investor data to observe any potential relationships. In order to assess chance, the scientists also did linear regression model simulations to look at trends there. The simulations, much like those done on the prayer problem in class, were used to see how many simulations resulted in similar results simply through chance.

The study found that there was a significant statiscal difference between the return made on investment during the regular moon phases and those made during the full moon phase. Behavior during the full moon tended to be more antagoinistic and less intellectual. In other words, smart financial men were ruled more by instinct during the full moon than otherwise. As always, this could be due to chance, a Type 1 error, or it could be correct. Confounding variables could also be involved here, but for the same reason we ruled out reverse causation in the previous blog, we must also do so here.

A Contrasting Study

“Does Full or New Moon Influence Stock Markets? : A Methodological Approach” looks at the same topic but finds a very different result. There are some benefits to this retrospective observational study, particularly its longevity. The study was conducted from 1962-1986. In my opinion, that makes the data a little stronger because it is supported over a long period rather than the two sessions examined in the previous study. Over this length of time rises and falls of the stock market were compared to when they occurred in the lunar cycle. The researchers used multiple indices to compare and found that p>.05 and the correlations were not statistically significant. Of course since it is a study and not an experiment, the data may not indicate a correlation (or lack thereof). Reverse causation can be ruled out, but chance cannot, leaving the results susceptible to a Type 2 error.

Quite simply the decision I had to make here was personal. Which data holds more weight in my opinion based on the study methodology and results? Is there even a mechanism that could conceivably link the moon and strange behavior?

A Possible Mechanism

So we have evidence both from my first blog and this one that show a correlation between the moon and strange behavior (with the exception of the last study mentioned above). We also have years of anecdotal evidence that points to a possible relationship between the two. The word lunatic literally means “moon sick.” What mechanism could possibly create this body of evidence? Over several sources I have noticed a common theme between papers. Particularly this one. Scientists seem to think that the same gravitational pull the moon has on the ocean also pulls on the water in the human body. Since we are over 50% water, scientists hypothesize that the body has mini tidal waves that throw our systems out of whack. This could be the cause of behavioral changes.

What to Take Away

After looking at all the evidence in this blog series, I have come to the conclusion that there is some evidence that the moon affects behavior. There are studies out there, like the one above, that say the moon has no effect on certain things, but they are only a small proportion of all the studies looking for correlations. In my eyes that indicates that those are Type 2 errors, although we shouldn’t discount the idea that the file drawer problem may be affecting these results. The presence of multiple studies showing a correlation between the moon and strange behavior leads me to think that the idea has a solid base. Although the mechanism is disputed, the section on tidal waves provides one possible explanation.

In conclusion:

The moon might very well alter your behavior, making you seem just a little crazy.

Let me know what you think of these findings. During the next full moon, pay attention to your

Some people during the full moon.

behavior and those around you. Are they acting differently? Do you agree with my conclusions? Let me know in the comments below. If you haven’t already, check out and comment on my previous blog by clicking here.